GNU bug report logs - #28469
xargs arguments are not passed to grep

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Sergiu Bordei <sergiu.bordei <at> gmail.com>
To: bug-grep <at> gnu.org
Subject: xargs arguments are not passed to grep
Date: Fri, 15 Sep 2017 11:47:46 +0200

[Message part 1 (text/plain, inline)]

Hello,

please find an error detected when is used a combination of "xargs" and
"grep", arguments {} are not substituted in grep construction:
expected results:
echo "inga"|grep -c "i"
1
user <at> box1:~$ a="i"; echo `echo "inga"|grep -c $a`
1

but was necessary tu use it in combination with xargs:

user <at> box1:~$ echo "i" | xargs -I{} echo $(echo {} ;a=$(echo {}) ; echo $a ;
echo "inga"|grep -c $a)
i i 0
user <at> box1:~$ echo "i" | xargs -I{} echo $(echo {} ;a=`echo {}` ; echo $a ;
echo "inga"|grep -c $a)
i i 0
user <at> box1:~$ echo "i" | xargs -I{} echo $(echo {} ;a={} ; echo $a ; echo
"inga"|grep -c $a)
i i 0
user <at> box1:~$ echo "i" | xargs  -I{} echo `echo {} ;a={} ; echo $a ; echo
"inga"|grep -c $a`
i i 0
user <at> box1:~$ echo "i" | xargs -I{} echo `echo {} ;a={} ; echo $a ; echo
"inga"|grep -c $a`
i i 0
user <at> box1:~$ echo "i" | xargs -I{} echo `echo {} ;a={} ; echo $a ; echo
"inga"|grep -c $a`
i i 0



Thanks,
Sergiu Bordei

[Message part 2 (text/html, inline)]

Message #8 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Paul Jackson <pj <at> usa.net>
To: bug-grep <at> gnu.org, sergiu.bordei <at> gmail.com
Subject: Re: bug#28469: xargs arguments are not passed to grep
Date: Fri, 15 Sep 2017 11:34:26 -0500

Sergiu wrote:
>> please find an error detected when is used a combination of "xargs" and
>> "grep", arguments {} are not substituted in grep construction:

I believe that all your examples, both expected (count of "1" resulting)
and apparently unexpected (outputs of "i i 0") are working as expected.

I am guessing (am I right?) that you were expecting outputs of "i i 1"
or some such from your last six more complex examples using xargs,
however that "echo inga | grep -c $a" is working on an $a value that
is still inside the $( ... ) or ` ... ` command substitution, and thus equal
to '{}', with $a not yet set to "i" by the final execution of the xargs
invocation of the output from that command substitution.

-- 
                Paul Jackson
                pj <at> usa.net

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